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Selfish Herd Theory
The selfish herd theory states that individuals within a population attempt to reduce their predation risk by putting other conspecifics between themselves and predators. A key element in the theory is the domain of danger, the area of ground in which every point is nearer to a particular individual than to any other individual. Such antipredator behavior inevitably results in aggregations. The theory was proposed by W. D. Hamilton in 1971 to explain the gregarious behavior of a variety of animals. It contrasted the popular hypothesis that evolution of such social behavior was based on mutual benefits to the population. The basic principle governing selfish herd theory is that in aggregations, predation risk is greatest on the periphery and decreases toward the center. More dominant animals within the population are proposed to obtain low-risk central positions, whereas subordinate animals are forced into higher risk positions. The hypothesis has been used to explain why populati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Predation
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the host) and parasitoidism (which always does, eventually). It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as seed predators and destructive frugivores are predators. Predators may actively search for or pursue prey or wait for it, often concealed. When prey is detected, the predator assesses whether to attack it. This may involve ambush or pursuit predation, sometimes after stalking the prey. If the attack is successful, the predator kills the prey, removes any inedible parts like the shell or spines, and eats it. Predators are adapted and often highly specialized for hunting, with acute senses such as vision, hearing, or smell. Many predatory animals, both vertebrate and inv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voronoi Diagram
In mathematics, a Voronoi diagram is a partition of a plane into regions close to each of a given set of objects. In the simplest case, these objects are just finitely many points in the plane (called seeds, sites, or generators). For each seed there is a corresponding region, called a Voronoi cell, consisting of all points of the plane closer to that seed than to any other. The Voronoi diagram of a set of points is dual to that set's Delaunay triangulation. The Voronoi diagram is named after mathematician Georgy Voronoy, and is also called a Voronoi tessellation, a Voronoi decomposition, a Voronoi partition, or a Dirichlet tessellation (after Peter Gustav Lejeune Dirichlet). Voronoi cells are also known as Thiessen polygons. Voronoi diagrams have practical and theoretical applications in many fields, mainly in science and technology, but also in visual art. The simplest case In the simplest case, shown in the first picture, we are given a finite set of points in the Euclidean p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sparrowhawk
Sparrowhawk (sometimes sparrow hawk) may refer to several species of small hawk in the genus ''Accipiter''. "Sparrow-hawk" or sparhawk originally referred to ''Eurasian sparrowhawk, Accipiter nisus'', now called "Eurasian" or "northern" sparrowhawk to distinguish it from other species. The American kestrel (''Falco sparverius''), a North American falcon species, is also commonly referred to as a "sparrow hawk". Hawk species include: {{Animal common name Accipiter Birds by common name ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Redshank
The common redshank or simply redshank (''Tringa totanus'') is a Eurasian wader in the large family Scolopacidae. Taxonomy The common redshank was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his ''Systema Naturae'' under the binomial name ''Scolopax totanus''. It is now placed with twelve other species in the genus ''Tringa'' that Linnaeus had introduced in 1758. The genus name ''Tringa'' is the New Latin name given to the green sandpiper by the Italian naturalist Ulisse Aldrovandi in 1603 based on Ancient Greek ''trungas'', a thrush-sized, white-rumped, tail-bobbing wading bird mentioned by Aristotle. The specific ''totanus'' is from , the Italian name for this bird. Six subspecies are recognised: * ''T. t. robusta'' ( Schiøler, 1919) – breeds in Iceland and the Faroe Islands; non-breeding around the British Isles and west Europe * ''T. t. totanus'' (Linnaeus, 1758) – breeds in west, north Europe to west Siberia; winters in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adelie Penguins
Adelie or Adélie may refer to: * Adélie Land, a claimed territory on the continent of Antarctica * Adelie Land meteorite Adelie Land is a meteorite discovered on December 5, 1912, in Antarctica by Francis Howard Bickerton (1889-1954), a member of Sir Douglas Mawson's Australasian Antarctic Expedition. It was named after Adélie Land and it was the first meteorite ..., a meteorite discovered on December 5, 1912, in Antarctica by Francis Howard Bickerton * Adélie penguin, a species of penguin common along the entire coast of the Antarctic continent * Adélie Valley, a drowned fjord on the continental margin of East Antarctica {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish School
In biology, any group of fish that stay together for social reasons are shoaling, and if the group is swimming in the same direction in a coordinated manner, they are schooling. In common usage, the terms are sometimes used rather loosely. About one quarter of fish species shoal all their lives, and about one half shoal for part of their lives. Fish derive many benefits from shoaling behaviour including defence against predators (through better predator detection and by diluting the chance of individual capture), enhanced foraging success, and higher success in finding a mate. It is also likely that fish benefit from shoal membership through increased hydrodynamic efficiency. Fish use many traits to choose shoalmates. Generally they prefer larger shoals, shoalmates of their own species, shoalmates similar in size and appearance to themselves, healthy fish, and kin (when recognized). The oddity effect posits that any shoal member that stands out in appearance will be preferen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Minnow
The Eurasian minnow, minnow, or common minnow (''Phoxinus phoxinus'') is a small species of freshwater fish in the carp family Cyprinidae. It is the type species of genus ''Phoxinus''. It is ubiquitous throughout much of Eurasia, from Britain and Spain to eastern Siberia, predominantly in cool () streams and well- oxygenated lakes and ponds. It is noted for being a gregarious species, shoaling in large numbers. Description The common minnow is a small fish which reaches a maximum total length of , but is normally around in length. It has 3 spines and 6–8 soft rays in its dorsal fin with 3 spines and 6–8 soft rays in its anal fin. Its spine is made up of 38–40 vertebrae. It is distinguished from similar species which occur in Europe by having the lateral line normally extending beyond the nase of the anal fin, by a line of vertically elongated blotches along the lateral line each with a depth equivalent to 1/3–1/2 of the body's depth at same position, these ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of living fish species are ray-finned fish, belonging to the class Actinopterygii, with around 99% of those being teleosts. The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey of arthropods. Mos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiddler Crab
The fiddler crab or calling crab may be any of more than one hundred species of semiterrestrial marine crabs in the family Ocypodidae, well known for their sexual dimorphism, sexually dimorphic claws; the males' major claw is much larger than the minor claw, while the females' claws are both the same size. A smaller number of ghost crab and mangrove crab species are also found in the family Ocypodidae. This entire group is composed of small crabs, the largest being slightly over two inches (5 cm) across. Fiddler crabs are found along sea beaches and brackish intertidal mud flats, lagoons, swamps, and various other types of brackish or salt-water wetlands. Like all crabs, fiddler crabs molting, shed their shells as they grow. If they have lost legs or claws during their present growth cycle, a new one will be present when they molt. If the large fiddle claw is lost, males will develop one on the same side after their next molt. Newly molted crabs are very vulnerable because o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convex Polygon
In geometry, a convex polygon is a polygon that is the boundary of a convex set. This means that the line segment between two points of the polygon is contained in the union of the interior and the boundary of the polygon. In particular, it is a simple polygon (not self-intersecting). Equivalently, a polygon is convex if every line that does not contain any edge intersects the polygon in at most two points. A strictly convex polygon is a convex polygon such that no line contains two of its edges. In a convex polygon, all interior angles are less than or equal to 180 degrees, while in a strictly convex polygon all interior angles are strictly less than 180 degrees. Properties The following properties of a simple polygon are all equivalent to convexity: *Every internal angle is strictly less than 180 degrees. *Every point on every line segment between two points inside or on the boundary of the polygon remains inside or on the boundary. *The polygon is entirely contained in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Snake (other)
Different snakes are called water snakes. "Water snake" is also sometimes used as a descriptive term for any snakes that spend a significant time in or near fresh water, such as any species belonging to the family Acrochordidae. They should not be confused with sea snakes, which live primarily or entirely in marine environments. Examples of snakes called water snakes include: *Family Boidae ** Green anaconda - Water boa *Family Colubridae ** ''Hydrodynastes'' species, including: ***'' Hydrodynastes gigas'' – false water snake or Brazilian smooth snake ** '' Natrix natrix'' ** ''Natrix tessellata'' ** '' Nerodia'' species ** ''Opisthotropis'' species ** '' Sinonatrix'' species, including: *** '' Sinonatrix percarinatus'' – eastern water snake ** '' Fowlea'' species, including: *** ''Fowlea piscator'' – Asiatic water snake or chequered keelback *Family Dipsadidae ** ''Helicops'' (snake) species, including: *** ''Helicops angulatus'' – brown-banded water snake ** ''Liophis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Risk
In simple terms, risk is the possibility of something bad happening. Risk involves uncertainty about the effects/implications of an activity with respect to something that humans value (such as health, well-being, wealth, property or the environment), often focusing on negative, undesirable consequences. Many different definitions have been proposed. The international standard definition of risk for common understanding in different applications is “effect of uncertainty on objectives”. The understanding of risk, the methods of assessment and management, the descriptions of risk and even the definitions of risk differ in different practice areas (business, economics, environment, finance, information technology, health, insurance, safety, security etc). This article provides links to more detailed articles on these areas. The international standard for risk management, ISO 31000, provides principles and generic guidelines on managing risks faced by organizations. Definitions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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